1. Field of the Invention
The present invention relates to a fluorescent lamp and a display apparatus having the fluorescent lamp.
2. Description of Related Art
In recent years, as a source of back light for liquid crystal display apparatuses used in personal computers and the like, a cold cathode-type fluorescent lamp, which has a long life and generates little heat, is widely used. In the fluorescent lamp, as shown in a diagrammatic cross-sectional view of FIG. 1(A), a glass tube 11 is sealed at both ends by a dumet wire 12 including, for example, a copper-clad iron alloy and bead glass 13. To the tip portion of the dumet wire 12 positioned inside of the glass tube 11 is fitted an electrode 14 comprising sintered metal obtained by sintering metal powder of tungsten or hafnium or a mixture thereof, and may also comprise nickel, niobium, or the like. A fluorescent particle layer 15 is formed on the inner surface of the glass tube 11, and the glass tube 11 is filled with a mixed rare gas, such as neon gas, argon and the like, and may have also have mercury dispersed therein.
In the production of the fluorescent lamp, generally, a fluorescent material slurry comprising a fluorescent particle mixture of blue light emitting fluorescent particles, red light emitting fluorescent particles, and green light emitting fluorescent particles is applied to the inner surface of a glass tube to form a fluorescent material slurry layer. There is a vast difference in specific gravity between the blue light emitting fluorescent particles, red light emitting fluorescent particles, and green light emitting fluorescent particles used. Therefore, if the fluorescent material slurry is applied to the inner surface of the glass tube, the difference of specific gravity between the fluorescent particles causes a difference in the state of flow between the blue light emitting fluorescent particles, the red light emitting fluorescent particles, and the green light emitting fluorescent particles in the fluorescent material slurry. In other words, the fluorescent particles having a higher specific gravity flow more quickly and the fluorescent particles having a lower specific gravity flow more slowly. Consequently, a difference is caused between the composition of the fluorescent particle mixture forming a portion of the fluorescent particle layer formed on the inner surface of the glass tube 11 at one end portion (hereinafter, for convenience sake, this mixture is frequently referred to as a “fluorescent particle mixture at one end portion of the glass tube”) and the composition of the fluorescent particle mixture forming a portion of the fluorescent particle layer formed on the inner surface of the glass tube 11 at another end portion (hereinafter, for convenience' sake, this mixture is frequently referred to as a “fluorescent particle mixture at another end portion of the glass tube”), so that a phenomenon occurs wherein the glass tube 11 has a difference in luminescent color between one end portion and another end portion. The difference between the fluorescent particle mixture at one end portion of the glass tube and the fluorescent particle mixture at another end portion of the glass tube is means a difference in the ratio of the blue light emitting fluorescent particles, the red light emitting fluorescent particles, and the green light emitting fluorescent particles at the respective end portions of the glass tube, and this meaning applies to the following descriptions. The above described difference in the luminescent color is recognized as an uneven display in the liquid crystal display apparatus.
[Patent document 1] Japanese Patent Application Publication (KOKAI) No. 2003-45329